Grid-Following DVI-Based Converter Operating in Weak Grids for Enhancing Frequency Stability

Abstract

Inertia requirement is the paramount challenge in future power systems with a significant share of renewable energy generators. A promising solution to this issue is applying Distributed Virtual Inertia (DVI) concept, i.e. releasing energy preserved in the DC-link capacitors of employed power converters in the grid following a frequency disturbance. Nonetheless, small-signal stability analyses affirm that a local mode associated with the control system is prone to become unstable when the grid-interactive converter augmented with the DVI operates in weak grids. To overcome this problem, an efficient compensator is proposed in this paper. This compensator introduces one degree-of-freedom to the direct-axis current controller in synchronous reference frame, which eliminates the adverse impact of DVI function on converter stability. Finally, the efficacy of the proposed control framework is depicted by simulations in MATLAB. The results illustrate that the grid frequency rate of change following a step-up load change is improved by 30% compared to the case in which the DVI loop is nullified.